The present invention generally relates to mounting of electronic components, and more particularly, to a mounting arrangement of a chip type component onto a printed circuit board, in which a chip type component having terminal electrodes at its end portions, such as a chip type multi-layer ceramic capacitor, chip type resistor or the like, is fixed by soldering it onto land portions on a printed circuit board, through cream type solder applied onto said land portions.
Commonly, a chip type component 4 such as the chip type multi-layer ceramic capacitor, chip type resistor, or the like as referred to above, includes, as shown in FIG. 4, a chip type component main body 1 in a rectangular cubic box-like configuration, and terminal electrodes 2 and 3 provided at opposite end portions of said main body 1 and, each extending from the end face of the main body 1 and across the side faces thereof neighboring said end face. These terminal electrodes 2 and 3 are intended to be directly soldered onto land portions of a printed circuit board when said chip type component is actually mounted onto said printed circuit board.
Conventionally, as shown in FIGS. 5 and 6, land portions 5 and 6 are formed on the printed circuit board P on which the chip type component 4 as in FIG. 4 is to be actually mounted, each having a size larger than an area of a portion where the terminal electrode 2 or 3 of the chip type component 4 overlaps the printed circuit board P, and the terminal electrodes 2 and 3 of the chip type component 4 are soldered onto said land portions 5 and 6. More specifically, with the cream type solder 7 applied over the land portions 5 and 6, said cream type solder 7 is melted again through heating, and by reflow soldering, for soldering the terminal electrodes 2 and 3 onto said land portions 5 and 6, such terminal electrodes 2 and 3 are respectively soldered onto the land portions 5 and 6.
A problem occurs in the case where the terminal electrodes 2 and 3 of the chip type component 4 are to be soldered to the printed circuit board P, having the land portions 5 and 6 as described above, by reflow soldering. The problem is that the chip type component 4 is undesirably floated or raised away from the printed circuit board in the process in which the cream type solder 7 is heated so as to be re-melted, before it is then solidified. The causes for giving rise to the above problem may be attributable to such factors, as the dimensions of the land portions 5 and 6 not being proper with respect to those of the terminal electrodes 2 and 3 of the chip type component 4j or the heat given to the cream type solder 7 applied over the land portions 5 and 6 during the reflow soldering not being uniform; or the amount of the applied cream type solder being different between the land portions 5 and 6; or a shift in the position of the chip type component 4 as compared with the cream type solder 7, etc.
By way of example, in the case where the sizes of the land portions 5 and 6 are large with respect to the sizes of the terminal electrodes 2 and 3 of the chip type component 4, surface tensions F1 and F2 acting on the terminal electrodes 2 and 3 of the chip type components 4, due to the cream type solder melted by heating, have component forces F11 and F21 acting perpendicularly to the opposite end faces of the chip type component 4 and directed away from said chip type component 4 as shown in FIG. 7. Thus, when a difference is produced between the above forces F11 and F21 due to a difference in the amount of the cream type solder 7 to applied with respect to the land portions 5 and 6, or due to a non-uniformity in heating the cream type solder 7, etc., a moment Mp tending to rotate the chip type component 4 in the direction, indicated by the arrow A1 about a corner portion B of the terminal electrode 2 acts on said chip type component 4. If this moment Mp exceeds a moment Mw due to the weight of the chip type component 4, then such floating or rising of said chip type component 4 takes place as described above. Therefore, such floating or rising occurs more frequently in a small sized chip type component with a light weight.